EP4161765B1 - Repair patch for an elastomer component with an improved connection layer - Google Patents

Description

TECHNICAL FIELD

The invention relates to a repair patch for an elastomer component, in particular for a vehicle tire, the use of the repair patch for repairing a damaged vehicle tire, and a method for connecting the repair patch to an elastomer component. The repair patch comprises in particular a connecting layer which, before vulcanization, contains a mixture of a first and a second natural rubber component, the mixture having a bimodal molecular weight distribution.

TECHNICAL BACKGROUND

In general, the repair of a damaged vehicle tire with minor punctures on the surface area is carried out using a so-called combination repair body. In the case of larger damage in the tread or sidewall area, however, the damaged area is worked out and the resulting so-called funnel is filled with raw rubber. The strength members interrupted in the damaged area are then bridged using a repair patch, which in turn contains corresponding strength members. Since the flow of force in the strength members of vehicle tires and repair patches must be transferred via the rubber layers in between, high demands are placed on the connecting layer between the vehicle tire and the repair patch in particular with regard to a secure and permanent bond to the vehicle tire.

In the known processes for installing a repair patch in a vehicle tire, two elements are required to create a permanent bond between To create a bond between the repair patch and the vehicle tire, an adhesive and the above-mentioned bonding layer of the repair patch.

The adhesive usually consists of natural rubber dissolved in solvent, resins and accelerators, which are required for the reaction, especially for vulcanization.

In the known repair processes for vehicle tires, the repair site is usually cleaned and roughened before the repair patch is applied in order to create an active surface with a high structure. In the next step, the adhesive is applied to the repair site. The solvent in the adhesive must then be allowed to evaporate. The repair patch is then placed on the repair site and pressed into place. Depending on the process selected, vulcanization then takes place without pressure at room temperature or by applying pressure and temperature using suitable devices (e.g. in an autoclave or in a heating press). The main disadvantage of this process is the time required for the solvent to evaporate.

In general, the adhesives currently in use are based on organic solvents, which can pose a risk to the environment and the health of the user. In some countries, some of these solvents are no longer allowed to be used to repair rubber objects.

Furthermore, the evaporation of the solvent is challenging, as the adhesion of the repair patch is highly dependent on the degree of evaporation. If the adhesive dries for too long, sufficient adhesion is no longer achieved (overdrying). On the other hand, if the drying or evaporation time is too short, there is still too much solvent on the repair site, so that the adhesion of the repair patch is not guaranteed, since the solvent remaining in the repair site leads to the formation of bubbles, particularly during vulcanization at low temperatures. When using flammable solvents, appropriate measures to prevent fires, e.g. by means of extraction and ventilation, are also necessary.

The bonding layer of a repair patch usually consists of masticated natural rubber and resins and does not contain any accelerators. The properties of conventional bonding layers are usually sufficient for standard applications. However, developments in the field of elastomer components, particularly in the vehicle tire sector, naturally also influence the requirements that will be placed on a repair patch in the future. For example, the tire coating or the roughened structure of the damaged area during the repair can vary greatly depending on the manufacturer or area of application.

From the EN 10 2009 050899 A1 is a repair patch for an elastomer component, in particular for a vehicle tire, 2. according to the preamble of claim 1, with a cover layer, a connecting layer for laying on a wall of the elastomer component, and at least one intermediate layer arranged between the connecting layer and the cover layer. Before vulcanization with the elastomer component, the connecting layer has such a ready-made tack that a connection between the repair patch and the elastomer component transfers at least the dead weight of the repair patch and the connecting layer has a separation value of at least 5 N/mm after vulcanization with the elastomer component.

The object of the invention is therefore to provide a repair patch and a method for connecting the repair patch to an elastomeric component, which make it possible to variably adjust the properties of the connecting layer, in particular adhesive strength and load strength, depending on an application.

THE SOLUTION OF THE PROBLEM

The object is solved with the features of independent claims 1 and 15. The dependent claims are directed to particular embodiments of the invention.

According to the invention, a repair patch for an elastomeric component, in particular for a vehicle tire, comprises a cover layer, a connecting layer for resting on a wall of the elastomeric component, and at least one intermediate layer arranged between the connecting layer and the cover layer.

According to the invention, the connecting layer contains a first and a second natural rubber component before vulcanization with the elastomer component, wherein the first natural rubber component has a lower molecular weight M _W than the second natural rubber component, such that a mixture of the first and the second natural rubber component has a bimodal molecular weight distribution. In this way, an adhesive strength of the connecting layer can be advantageously adjusted via the first natural rubber component and a load strength of the connecting layer can be adjusted via the second natural rubber component.

Bimodal here means a distribution that has two modes or maxima. A bimodal distribution can be both symmetrical and asymmetrical. According to the invention, the bimodal molecular weight distribution (molar mass distribution) results from the proportional superposition of the two unimodal (one mode, one maximum) molecular weight distributions of the first and second natural rubber components. The maximum of the unimodal molecular weight distribution of the first natural rubber component is at a lower molecular weight than that of the second natural rubber component. In other words, according to the invention, the first natural rubber component has a maximum in the unimodal molecular weight distribution that is at a lower molecular weight than that of the second natural rubber component.

The values given here refer to the so-called mass average M _W. The bimodal molecular weight distribution is thus described by the distribution of a weight fraction depending on the molecular weight.

According to the invention, natural rubber is used in the connecting layer. Structurally, natural rubber is a cis-1,4-polyisoprene, which is produced by polymerization of isoprene monomers:

Natural rubbers belong to the group of so-called elastomers. Elastomers are loosely linked polymers that exhibit rubber-elastic behavior. Elastomers can be cross-linked directly during polymerization or later through vulcanization.

In a preferred embodiment, the first natural rubber component can have a molecular weight of M _w = 1 × 10 ⁶ g/mol. In a further preferred embodiment, the second natural rubber component can have a molecular weight of M _w = 2 × 10 ⁶ g/mol. The molecular weight can be determined in both embodiments by diffusion sedimentation and/or osmosis. In particular, commercially available products with corresponding molecular weights can be used according to the invention. For example, commercially available natural rubber with a constant low viscosity can be used as the first natural rubber component, which is generally produced by blending rubber sap from trees to form latexes, felling with acid to form rubber crumbs and pressing into bales. For example, natural rubber with a constant high viscosity, such as the RSS1 or RSS3 type, can be used as the second natural rubber component.

Since natural rubber, as a natural product, contains insoluble gel components, the molecular weight of natural rubber is often difficult to determine. Alternatively or additionally, the so-called Mooney viscosity can therefore be used for characterization. In this case, two polymers of the same type whose Mooney viscosities are significantly different can also be clearly distinguished in terms of molecular weight. In a preferred embodiment, a Mooney viscosity of the first natural rubber component and the second natural rubber component can therefore differ by at least a factor of 2. In a particularly preferred embodiment, the Mooney viscosity ML=1+4/100°C of the first natural rubber component can be 35 - 40 MU. In a further preferred embodiment, the Mooney viscosity ML=1 +4/100°C of the second natural rubber component can be 70-90 MU. The Mooney viscosity can be determined, for example, according to DIN 53523.

According to the invention, there is no restriction as to whether the first and/or the second natural rubber component is a single natural rubber or a mixture of natural rubbers whose molecular weight M _W is in the low or high range, respectively. In a preferred embodiment, however, the first natural rubber component and/or the second natural rubber component can consist of a mixture of natural rubbers. In a further preferred embodiment, the first natural rubber component and/or the second natural rubber component can consist of a single natural rubber.

According to the invention, the proportion of the first and second natural rubber components in the mixture is not restricted. In a preferred embodiment, a proportion of the first natural rubber component can be 25-50% by weight based on the total mass of the first and second natural rubber components, and a proportion of the second natural rubber component can be 50-75% by weight based on the total mass of the first and second natural rubber components, but particularly preferably the proportion of the first natural rubber component can be 35-45% by weight and the proportion of the second natural rubber component 55-65% by weight, but very particularly preferably the proportion of the first natural rubber component can be 44% by weight and the proportion of the second natural rubber component 56% by weight. In this way, good adhesive strength can be ensured with improved load strength at the same time.

Furthermore, in a preferred embodiment, the connecting layer can additionally contain a filler system of precipitated silica 5-15%, silica 20-30% and dye. In addition, in a further preferred embodiment, the connecting layer can contain at least 2% sulfur. The proportions each correspond to wt.% based on the total mass of the connecting layer. During vulcanization, the first and second natural rubber components can be cross-linked with one another using sulfur:

In a further preferred embodiment, a removable protective film can also be provided which protects the connecting layer from contamination until it is used.

In a further preferred embodiment, the intermediate layer can comprise a plurality of fibrous inserts arranged in a substantially structured manner.

According to the invention, the repair patch described above can be used to repair a damaged vehicle tire.

According to the invention, a method for connecting the repair patch described above to an elastomeric component comprises the step of producing a connecting layer containing a first and a second natural rubber component, wherein the first natural rubber component has a lower molecular weight, M _W , than the second natural rubber component, such that a mixture of the first and the second natural rubber component has a bimodal molecular weight distribution. The connecting layer is produced according to the invention by: (a) homogenizing the second natural rubber component in an internal mixer; (b) removing the second natural rubber component again; and (c) mixing the first and the homogenized second natural rubber component. The method according to the invention further comprises the step of providing the elastomeric component; the step of attaching the repair patch to the elastomeric component via the connecting layer, in particular at a repair site; and the step of vulcanizing the repair patch on the elastomeric component.

In a preferred embodiment, in step c) of producing the connecting layer, the first and the homogenized second natural rubber component can be additionally mixed with a filler system containing a precipitated silica 5-15%, silica 20-30% and dye, and at least 2% sulfur.

SHORT DESCRIPTION OF THE CHARACTERS

• Figure 1 shows schematically a sectional view of a repair patch for a vehicle tire according to an embodiment.
• Figure 2 shows schematically a bimodal molecular weight distribution resulting from the superposition of two unimodal molecular weight distributions of a first and a second natural rubber component.
• Figure 3 shows a block diagram of a portion of a method for bonding a repair patch to an elastomeric component according to an embodiment.
• Figure 4 shows a bar diagram regarding the different adhesion strength of a bonding layer with natural rubber in unimodal and bimodal molecular weight distribution.
• Figure 5 shows a bar chart regarding the structural resistance of a bonding layer with natural rubber in unimodal and bimodal molecular weight distribution.

DETAILED DESCRIPTION OF THE FIGURES AND PREFERRED EMBODIMENTS

In the following, examples or embodiments of the present invention are described schematically with reference to the attached figures. It should be emphasized that the present invention is in no way limited to the embodiments described below and their The invention is not limited or restricted to the specific embodiment features, but also includes modifications of the embodiments, in particular those which are included within the scope of protection of the claims by modifying the features of the examples described or by combining individual or multiple features of the examples described.

Referring to Fig.1 a repair patch 1 for vehicle tires according to the present invention is shown schematically. On the top of the repair patch 1, a cover layer 10 is formed, which has no adhesive properties before and after the repair. An intermediate layer 20 is formed adjacent to the cover layer 10. In a preferred embodiment, the intermediate layer 20 can have a plurality of fibrous inserts 70. These inserts 70 can be arranged in one or more layers over the thickness of the intermediate layer 20, wherein each individual layer can have a structural arrangement of the fibrous inserts 70. The orientation of the individual layers in the intermediate layer 20 can be different from one another. In particular in the case of major damage in the tread or sidewall area, these inserts 70 can serve to bridge the strength members interrupted in the area of damage.

The connecting layer 30 is formed on the underside of the repair patch 1 and is in contact with the wall 80 of the vehicle tire during and after the repair. Furthermore, the connecting layer 30 is in contact with a raw rubber mass 50 before and after the vulcanization of the vehicle tire. The connecting layer 30 and its special properties are described below with reference to the Figure 2 described in detail.

As part of the repair of the damaged vehicle tire, the damaged area of the vehicle tire is roughened so that dust and dirt are removed and an undamaged layer of the components contained in the vehicle tire is exposed, whereby a substantially conical design for a repair point 60 in the vehicle tire is formed. The Repair site 60 filled with the raw rubber compound 50 before vulcanization of the bonding layer 30.

The repair patch 1 is then placed on the repair site 60, with its dimensions being selected such that the repair site 60 is completely covered by it. Furthermore, the dimensions of the repair patch 1 should be selected such that the tire wall 80 is sufficiently covered by the connecting layer 30 for a stable connection. The repair patch 1 can, for example, be preheated to an appropriate joining temperature.

After the repair patch 1 has been rolled on, the repair site 60 and the repair patch 1 are vulcanized under pressure and temperature by means of a suitable device or in an autoclave.

In a preferred embodiment, a removable protective film can also be provided which protects the connecting layer 30 from contamination until it is used.

The structure of the vehicle tire is shown here as an example for the sidewall area of a radial truck tire in such a way that the wall 80 of the vehicle tire is formed by the inner liner 90, to which the carcass 100 adjoins, which has the cord 120 in the form of an insert. Adjacent to the carcass 100 is the sidewall rubber 110 of the vehicle tire.

Referring to Figure 2 is a schematic representation of a bimodal molecular weight distribution (solid line) from the superposition of two unimodal molecular weight distributions for a first (dashed line) and a second (dotted line) natural rubber component. As can be seen from Figure 2 As can be seen, the first natural rubber component has a lower molecular weight M _W than the second natural rubber component, which can be seen from the position of the maximum. Both the first and the second natural rubber component have a unimodal molecular weight distribution. This results from the fact that Natural rubber generally always has a certain molecular weight distribution; the width of the curve can be an indicator of the purity or quality of the natural rubber.

If the first and second natural rubber components are mixed together, the bimodal molecular weight distribution results from the superposition of the two unimodal molecular weight distributions according to the mixture proportions. The position of the two maxima in the bimodal molecular weight distribution is also determined by the difference between the maxima of the unimodal molecular weight distributions. If, for example, the maxima of the two unimodal molecular weight distributions are close to one another, i.e. the first and second natural rubber components have molecular weights that are close to one another, this is also reflected in the bimodal distribution. The same applies in the opposite case. According to the invention, a bimodal molecular weight distribution is therefore bimodal as long as two maxima can be identified. In a preferred embodiment, however, the first natural rubber component can have a molecular weight of M _W = 1 × 10 ⁶ g/mol. In a further preferred embodiment, the second natural rubber component can have a molecular weight of M _W = 2 × 10 ⁶ g/mol. The molecular weight can be determined in both embodiments by diffusion-sedimentation and/or osmosis.

Since natural rubber as a natural product contains insoluble gel components, the molecular weight of natural rubber is often difficult to determine. Alternatively or additionally, the so-called Mooney viscosity can therefore be used for characterization. In a preferred embodiment, a Mooney viscosity of the first natural rubber component and the second natural rubber component can therefore differ by at least a factor of 2. In a particularly preferred embodiment, the Mooney viscosity ML=1+4/100°C of the first natural rubber component can be 35 - 40 MU. In a further preferred embodiment, the Mooney viscosity can ML=1 +4/100°C of the second natural rubber component is 70-90 MU. The Mooney viscosity can be determined according to DIN 53523, for example.

As also from Figure 2 As can be seen, the adhesive strength of the connecting layer can be adjusted via the proportion of the first natural rubber component and the load strength via the second natural rubber component. According to the invention, the proportion of the first and second natural rubber components in the mixture is not restricted. In a preferred embodiment, however, a proportion of the first natural rubber component can be 25-50 wt.% based on the total mass of the first and second natural rubber components, and a proportion of the second natural rubber component can be 50-75 wt.% based on the total mass of the first and second natural rubber components; particularly preferably, however, the proportion of the first natural rubber component can be 35-45 wt.% and the proportion of the second natural rubber component can be 55-65 wt.%; very particularly preferably, however, the proportion of the first natural rubber component can be 44 wt.% and the proportion of the second natural rubber component can be 56 wt.%. However, it is advantageous to give greater importance to the adhesive strength, so that the proportion of the first natural rubber component will be selected in such a way that the adhesive strength is good even with increased load strength.

According to the invention, there is no restriction as to whether the first and/or the second natural rubber component is a single natural rubber or a mixture of natural rubbers. As already mentioned above, natural rubber, considered as a single component, generally always has a certain molecular weight distribution. However, this also applies to mixtures of two or more individual natural rubbers, which can be produced in such a way that they have a corresponding unimodal molecular weight distribution. In a preferred embodiment, the first natural rubber component and/or the second natural rubber component can therefore consist of a mixture of natural rubbers. In a further preferred embodiment, the first natural rubber component and/or the second natural rubber component consist of a single natural rubber.

Furthermore, in a preferred embodiment, the connecting layer 30 may additionally contain, in addition to the first and second natural rubber components, a filler system consisting of a precipitated silica 5-15%, silica 20-30% and dye.

Furthermore, in a further preferred embodiment, the connecting layer can contain at least 2% sulfur. During vulcanization, the first and second natural rubber components can thus be crosslinked via sulfur bridges.

Referring to the Figure 3 A part of a method for bonding a repair patch to an elastomeric component according to an embodiment is described below. As in Figure 3 As can be seen, in order to produce a connecting layer containing a first and a second natural rubber component, the first natural rubber component having a lower molecular weight M _W than the second natural rubber component, such that a mixture of the first and the second natural rubber component has a bimodal molecular weight distribution, the second natural rubber component is first homogenized in an internal mixer in step S101. After homogenization, the second natural rubber component is removed from the internal mixer again in step S102. The now homogenized second natural rubber component is then mixed with the first natural rubber component. According to the Figure 3 In the embodiment shown, in step S103, the homogenized second natural rubber component can be mixed with the first natural rubber component, the filler system described above and at least 2% sulfur.

The information relating to Figure 3 The steps described are part of the method according to the invention, which further comprises the following steps: providing an elastomeric component; attaching the repair patch to the elastomeric Component over the bonding layer, particularly at a repair site, and vulcanization of the repair patch to the elastomeric component.

The advantages of the present invention will now be described with reference to the Figures 4 and 5 The repair patch and the method described herein make it possible in particular to tailor the properties of the bonding layer due to the bimodal molecular weight distribution of the two natural rubber components with regard to the compatibility of the repair patch with different tire casings or different roughened structures of damage areas. As can be seen from the Figures 4 and 5 As can be seen, the mixture of the first and the second natural rubber component with a bimodal molecular weight distribution not only has an improved adhesive strength compared to a unimodal distribution in the natural rubber component, but at the same time also has an improved structural resistance. In other words, a connecting layer which has a bimodal molecular weight distribution by mixing a first and a second natural rubber component shows an improved ability to bond to roughened surfaces due to the proportion of natural rubber with a low molecular weight, whereas an increased structural resistance of the connecting layer can be achieved due to the proportion of natural rubber with a high molecular weight, which results in improved aging resistance.

LIST OF REFERENCE SYMBOLS

• 1 repair patch
• 10 Top layer
• 20 Intermediate layer
• 30 Connection layer
• 40 elastomeric component
• 50 Raw rubber mass
• 60 Repair point
• 70 Fibrous inserts
• 80 wall
• 90 innerliners
• 100 carcass
• 110 Sidewall rubber of the vehicle tire
• 120 cord

Claims (16)

1. Repair patch (1) for an elastomeric component (40), in particular for a vehicle tyre, comprising:

   a cover layer (10),

   a connecting layer (30) for resting on a wall (80) of the elastomeric component (40), and

   at least one intermediate layer (20) arranged between the connecting layer (30) and the cover layer (10),

   characterised in that

   the connecting layer (30) contains a first and a second natural rubber component before vulcanization with the elastomeric component (40), wherein the first natural rubber component has a lower molecular weight M_W than the second natural rubber component, such that a mixture of the first and the second natural rubber component has a bimodal molecular weight distribution.
2. Repair patch (1) according to claim 1, wherein a Mooney viscosity of the first natural rubber component and of the second natural rubber component differs at least by a factor of 2.
3. Repair patch (1) according to claim 2, wherein the Mooney viscosity ML=1+4/100°C of the first natural rubber component is 35 - 40 MU.
4. Repair patch (1) according to claim 2 or 3, wherein the Mooney viscosity ML=1+4/100°C of the second natural rubber component is 70 - 90 MU.
5. Repair patch (1) according to at least one of claims 1 to 4, wherein the first natural rubber component and/or the second natural rubber component consist of a mixture of natural rubbers.
6. Repair patch (1) according to at least one of claims 1 to 5, wherein the first natural rubber component and/or the second natural rubber component consist of a single natural rubber.
7. Repair patch (1) according to at least one of claims 1 to 6, wherein the first natural rubber component has a molecular weight of M_W = 1 × 10⁶ g/mol, and wherein the molecular weight is determined by diffusion sedimentation and/or osmosis.
8. Repair patch (1) according to at least one of claims 1 to 7, wherein the second natural rubber component has a molecular weight of M_W = 2 × 10⁶ g/mol, and wherein the molecular weight is determined by diffusion sedimentation and/or osmosis.
9. Repair patch (1) according to at least one of claims 1 to 8, wherein a proportion of the first natural rubber component is 25-50% by weight based on the total mass of the first and the second natural rubber component, and a proportion of the second natural rubber component is 50-75% by weight based on the total mass of the first and the second natural rubber component.
10. Repair patch (1) according to at least one of claims 1 to 9, wherein the connecting layer (30) additionally contains a filler system of a precipitated silica 5-15%, silica 20-30% and dye.
11. Repair patch (1) according to at least one of claims 1 to 10, wherein the connecting layer (30) contains at least 2% sulfur.
12. Repair patch (1) according to at least one of claims 1 to 11, wherein a peelable protective film is provided which protects the connecting layer (30) from soiling until it is used.
13. Repair patch (1) according to at least one of claims 1 to 12, wherein the intermediate layer (20) has a plurality of substantially structured fibrous inserts (70).
14. Use of a repair patch (1) according to at least one of claims 1 to 13 for repairing a damaged vehicle tyre.
15. Method for connecting a repair patch (1) according to at least one of claims 1 to 13 to an elastomeric component (40), comprising the steps of:

    producing a connecting layer (30) containing a first and a second natural rubber component, wherein the first natural rubber component has a lower molecular weight M_W than the second natural rubber component, such that a mixture of the first and the second natural rubber component has a bimodal molecular weight distribution, by:

    (a) homogenizing (S101) the second natural rubber component in an internal mixer;

    (b) removing (S102) the second natural rubber component; and

    (c) mixing (S103) the first and the homogenized second natural rubber component;

    providing the elastomeric component (40);

    attaching the repair patch (1) to the elastomeric component (40) via the connecting layer (30), in particular at a repair point (60); and

    vulcanizing the repair patch (1) on the elastomeric component (40).
16. Method according to claim 15, wherein in step c) of producing the connecting layer the first and the homogenized second natural rubber component are additionally mixed with at least 2% sulfur, and a filler system containing a precipitated silica 5-15%, silica 20-30% and dye.

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